1. Field of the Invention
The present invention relates to antenna modules including an antenna element, an IC chip, and a multilayer body in or on which the antenna element and the IC chip are provided.
2. Description of the Related Art
An antenna module of this type is disclosed in, for example, Japanese Patent No. 4997779 identified below. This antenna module includes a multilayer body in which a plurality of insulative bases are stacked up in a predetermined direction. On the surface of each base, a spiral-shaped coil pattern is provided. The coil patterns which are adjacent to each other in a predetermined direction are coupled to each other by a via conductor, whereby an antenna element is formed. Here, a retreat layout is provided such that the via conductor is positioned near a corner of the multilayer body, while a retreat layout is not provided at at least one of the other corners than the corner of the retreat layout.
Each insulative base is typically made of a resin or ceramic material. The coil pattern and via conductor are made of a metal material, such as copper. In general, metal materials undergo a small thermal deformation as compared with resin and ceramic materials. Therefore, in a compression and heating step which is part of the antenna module manufacturing process, stress is likely to occur at the location of the via conductor.
To increase the quantity of turns of the coil pattern, the gap between adjacent turns has been decreasing. In some cases, a base having a smaller thickness is used for decreasing the thickness of the entire module. Under such circumstances, the base is first softened in the heating step, and therefore, in some cases, strain or cracks occur in the base due to the via conductor which undergoes a small deformation. Further, thereafter, if the via conductor is softened to flow into the strain or cracks of the base, it can cause disconnection, or short circuit between adjacent turns.